Add feature flag to enable heterogenous features

[varungup90]

🚀 Feature Description and Motivation

Right now heterogenous feature such as optimizer or request tracing is enabled by default. Enabling by default has two issues 1) It add small performance penalty 2) Requires to enable include_usage for streaming.

Goal here is to add a feature flag which can fix both issues. Along with feature flag add support for request tracing for streaming.

Use Case

GPU Optimizer

Proposed Solution

No response

[varungup90]

cc @zhangjyr

[varungup90]

This is completed.